1. Field of the Disclosure
This disclosure generally relates to a human interface device and, more particularly, to an optical finger mouse and a physiological characteristic detection device that may simultaneously detect a physiological characteristic of a user, a finger displacement and a finger contact status.
2. Description of the Related Art
As the optical finger mouse has a relatively small size, it is very suitable for being applied to portable electronic devices. An optical finger mouse can be used to detect an intensity variation of reflected light from a finger surface of a user so as to identify a finger contact status and a finger displacement with respect to a touch surface. However, with the development of industry, users spend more and more time on utilizing portable electronic devices that puts a lot of stress on their bodies. Therefore, if a portable electronic device also has the function of detecting physiological characteristics of a user and is able to give a warning when necessary, the overuse of the portable electronic devices can then be avoided.
Conventional pulse oximeters utilize a noninvasive method to monitor the blood oxygenation and the heart rate of a user. The conventional pulse oximeters generally emit a red light beam (wavelength of about 660 nm) and an infrared light beam (wavelength of about 910 nm) to penetrate a part of the human body and detects an intensity variation of the penetrating light based on the feature of the oxyhemoglobin and deoxyhemoglobin having different absorptivities in particular spectrum, e.g. referring to U.S. Pat. No. 7,072,701 and entitled “Method for spectrophotometric blood oxygenation monitoring”. After the intensity variations of the penetrating light of the two wavelengths are detected, the blood oxygenation can be calculated according to equation (1):Oxygen saturation=100%[HbO2]/([HbO2]+[H])  (1)
wherein [HbO2] is oxyhemoglobin concentration; and [Hb] is deoxy-hemoglobin concentration.
Generally, the intensity variation of the penetrating light of the two wavelengths detected by a pulse oximeter is similar to FIG. 1. This is because blood vessels will expand and contract with heartbeats such that the blood volume that the light beams pass through will change to accordingly change the ratio of light energy being absorbed. Therefore, the absorptivity of blood of different light spectra can be calculated according to the intensity information changing continuously so as to calculate the physiology information, such as an oxyhemoglobin concentration and a deoxyhemoglobin concentration respectively. Finally, the blood oxygenation can be calculated according to equation (1).
However, as conventional pulse oximeters detect the intensity variation of the penetrating light, different intensity signals will be detected by detecting different parts of the human body. In addition, when the part of the human body being detected has a movement, a disturbed signal will be detected such that it is not possible to calculate correct physiological characteristics. Therefore, conventional pulse oximeters cannot be applied to portable electronic devices.
Accordingly, the present disclosure provides an optical finger mouse and a physiological characteristic detection method that may simultaneously detect physiological characteristics of a user, a finger displacement and a finger contact status, and can eliminate the signal noise caused by the movement.